As computer technology continues to advance, electronic components such as central processing units (CPUs) of computers are made to provide faster operational speed and greater functional capabilities. When a CPU operates at a high speed in a computer enclosure, its temperature increases greatly and dramatically. It is desirable to dissipate the generated heat quickly, for example, by using a heat sink attached to the CPU in the enclosure. This allows the CPU and other electronic components in the enclosure to function within their normal operating temperature ranges, thereby assuring the quality of data management, storage and transfer. Generally, a locking device is required for mounting the heat sink to the CPU.
FIG. 11 show a conventional locking device for mounting a heat sink 50′ to a CPU mounted on a printed circuit board. The locking device comprises a pair of clips 40′ and a retention module 60′. Each clip 40′ comprises a pair of locking legs 44′. Each locking leg 44′ defines a locking opening 46′ and a slot 48′ adjacent to the locking opening 46′. The heat sink 50′ comprises a pair of shoulders 52′ formed at opposite side portions thereof. The retention module 60′ is mounted on the printed circuit board and surrounds the CPU. The retention module 60′ comprises four of barbs 62′ formed at four corners thereof. In assembly, the heat sink 50′ is placed on the CPU. The pair of clips 40′ are placed on the shoulders 52′. The locking opening 46′ in one locking leg 44′ of each clip 40′ is engaged with the corresponding barb 62′ of the retention module 60′. Tool is inserted into the slot 48′ in the other locking leg 44′ to pivot the other locking leg 44′ outwardly to allow the corresponding locking opening 46′ to engage with the corresponding barb 62′ of the retention module 60′ to thereby secure the heat sink 50′ to the CPU. In disassembly, tools are required to pivot the locking legs 44′ outwardly to have the legs 44 released from the corresponding barbs 62′. However, it is inconvenient to use tools in assembly or disassembly. Furthermore, each clip 40′ is integrally formed and therefore has a large rigidity. As a result, large force is needed in operation.